2003/08/22
Shaffer -
grade 0 - closed; slit - 5 degrees or less; grade 1 - 10 degrees; grade II - 20
degrees; grade III - 30 degrees, grade IV-40 degrees
Spaeth classification system is most complete. describes geometric
angle of iris insertion, point of iris insertion on corneoscleral
wall, and shape of the peripheral iris.
Extent of TM pigmentation is also graded.
letters for iris insertion A ant to E posterior
A - ant to TM
B - to TM
C - scleral spur
D - full ciliary body
E - very deep
curvature of peripheral iris
R - regular, slight anterior bowing of iris
S - steep, marked convex curvature, sig
risk for angle closure, seen in plateau iris
Q - queer, concavity of peripheral iris, often seen in pigment
dispersion - backward bowing
(C)D - parenthesis is for what you see with no indentation
What is an occludable angle?
angles with inlets <10 to 15 degrees are potentially occludable. Angles c
inlets of 20 degrees should be watched for further narrowing with progressing
age
also, angles with high plateau configuration
occludable angle
while 2% of caucasians are believed to have
an occludable angle, only about 0.1% have an acute
angle attack. Chronic angle closure,
however, is more common.
approx. 2 to 5% of pop with potentially occludable
angle. demographics
of study population is important. older population more likely to have occludable
angle because angle narrows with angle.
Asians, in particular Eskimos, are more likely to have occludable angles and angle closure.
angle closure glc
caused by the anatomic closure of the tm by the iris.
90% of angle
closures is caused by pupillary
block
with pupillary block, the development of
acute vs. chronic angle closure depends on:
speed of which puillary block occurs
percentage of agnle involved
flaccidity of peripheral iris
width and depth of angle
types of 1o angle closure
acute - dramatic, violent attack
subacute - intermittent attacks
of milder degree
chronic - silent, gradual closure of angle
CHRONIC
ANGLE CLOSURE
portions of angle are permanently closed by PAS
plateau iris syndrome
describes iris root which angulates forward
sharply then flattens centrally
schwalbe's line - nonpig tm - pig tm - scleral spur
- ciliary face
treatment goals - in pupillary block - iridotomy or iridectomy
MEdical therapy should be initiated first
hyperosmotic agents - remove fluid
from vitreous lowering IOP
may also allow posterior movement of lens deepening ac
pressure lowering begins within 30 min and lasts 5-6 hours
isosorbide (1.5 to 2 g/kg), good
oral choice, not metabolized
mannitol - ok in DM, given IV
over 45 minutes is usually very effective - Cr cutoff is 2
carbonic anhydrase
acetazolamide, highly effective in
lowering IOP
with oral treatment maximal response at 2o, high plasma conc. for 4 to
6o
IV dose of
500 mg sig faster, rapid reduction in aq. inflow may help reverse pupillary
block
ADMINISTER pilocarpine 1 or 2% after
- if attack nor broken following pilocarpine,
then suspect lens related angle closure or synechial
closure. stop pilo, attempt iridotomy if cornea
allows. if
clarity poor attempt iridoplasty.
management of fellow eye
- prophylactic iridotomy in fellow eye
x in rare instance when angle is deep
- chance of angle closure in fellow eye is as high as 75% over
next 5-10 years